I was a little frustrated today to find out the line work tool does not work in perspective views (Revit 2008). I was happier to see just now that this has been fixed in Revit 2009 build 20080602_1900.
The work around I had to use today with the above problem, I had promised myself I would never use. Because in perspective views the filled regions or masking regions tools don’t work, I had to go into the plot sheet and cover the undesired line with a white line. First and last time I hope.